I. Field
The disclosure relates to the field of wireless communications and processing of wireless communication signals. More particularly, the disclosure relates to Fast Fourier Transform (FFT) processing of Orthogonal Frequency Division Multiplex (OFDM) signals.
II. Background
Orthogonal Frequency Division Multiplex (OFDM) is a multi-carrier modulation technique that effectively partitions the overall system bandwidth into multiple (N) orthogonal subbands. These subbands may also be referred to as tones, subcarriers, bins, and frequency channels. With OFDM, each subband is associated with a respective subcarrier that may be modulated with data.
In a wireless communication system, a radio frequency (RF) modulated signal may travel via a number of signal paths from a transmitter to a receiver. If the signal paths have different delays, then the received signal at the receiver would include multiple instances of the transmitted signal with different gains and delays. This time dispersion in the wireless channel causes frequency selective fading, which is characterized by a frequency response that varies across the system bandwidth. For an OFDM system, the N subbands may thus experience different effective channels and may consequently be associated with different complex channel gains.
The processing of OFDM systems can be considerably more involved compared to processing of received signals in other communication systems. The large amount of processing required puts a large burden on the receiver, in terms of processing capabilities. An ability to increase the processing capabilities in an OFDM receiver is desirable to allow for greater proliferation of communication systems utilizing the modulation scheme.